CN107810425A - Eliminate non-T2The T of weighted signal contribution2Weight MR imagings - Google Patents

Eliminate non-T2The T of weighted signal contribution2Weight MR imagings Download PDF

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CN107810425A
CN107810425A CN201680022551.5A CN201680022551A CN107810425A CN 107810425 A CN107810425 A CN 107810425A CN 201680022551 A CN201680022551 A CN 201680022551A CN 107810425 A CN107810425 A CN 107810425A
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CN107810425B (en
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J·P·格伦
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Koninklijke Philips NV
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
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    • G01R33/50—NMR imaging systems based on the determination of relaxation times, e.g. T1 measurement by IR sequences; T2 measurement by multiple-echo sequences
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    • A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves 
    • A61B5/055—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves  involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/48—NMR imaging systems
    • G01R33/4816—NMR imaging of samples with ultrashort relaxation times such as solid samples, e.g. MRI using ultrashort TE [UTE], single point imaging, constant time imaging
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    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
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    • G01R33/48—NMR imaging systems
    • G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
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    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/48—NMR imaging systems
    • G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
    • G01R33/56—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution
    • G01R33/5602—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution by filtering or weighting based on different relaxation times within the sample, e.g. T1 weighting using an inversion pulse

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Abstract

The present invention relates to the method that one kind carries out MR imagings to the object being located in the inspection volume of MR equipment (1).The purpose of the present invention is to realize to there is no to come from do not have T2The T of the interference contribution of the MR signals of weighting2Weight MR imagings.The method of the present invention comprises the following steps：A) object (10) is made to be subjected to the first T2Prepare sequence (T2PREP1), the first T2Preparing sequence includes excitation RF pulses (21), one or more refocusing RF pulses (22) and digs RF pulses (23)；B) object (10) is made to be subjected to the first reading sequence (RO1), described first, which reads sequence, includes the magnetic field gradient of at least one excitation RF pulses and shear, for gathering the first set of MR signals；C) object (10) is made to be subjected to the 2nd T2Prepare sequence (T2PREP2), the 2nd T2Preparing sequence includes excitation RF pulses (21 '), one or more refocusing RF pulses (22 ') and digs RF pulses (23 '), wherein, the 2nd T2Prepare sequence (T2PREP2) the RF pulses (21 ', 22 ', 23 ') in it is at least one have and the first T2Prepare the different phase of the corresponding RF pulses (21,22,23) of sequence (T2PREP1)；D) object (10) is made to be subjected to the second reading sequence (RO2), described second, which reads sequence, includes the magnetic field gradient of at least one excitation RF pulses and shear, for gathering the second set of MR signals；E) MR images are rebuild according to the first set of MR signals and the second set.In addition, the present invention relates to a kind of MR equipment and a kind of computer program for MR equipment.

Description

Eliminate non-T2The T of weighted signal contribution2Weight MR imagings
Technical field
The present invention relates to magnetic resonance (MR) imaging field.It is related to the method for MR imagings.The invention further relates to MR equipment and The computer program to be run in MR equipment.
Background technology
MR side is formed using the image for interacting to be formed two dimension or 3-D view between magnetic field and nuclear spin Method is used widely now, and especially in area of medical diagnostics, because for the imaging to soft tissue, they are being permitted Many-side is better than other imaging methods, it is not necessary to ionising radiation and not usually invasive.
According to common MR methods, to check that the body of patient is disposed in strong uniform magnetic field (B0) in, it is described strong The direction of uniform magnetic field define the axle (be usually z-axis) of the coordinate system that measurement is based on simultaneously.Depending on application can be passed through Electromagnetism alternating field (the RF fields, also referred to as B of defined frequency (so-called Larmor frequencies or MR frequencies)1) (spin is altogether for excitation Shake) magnetic field intensity, magnetic field produce for individual nuclear spin different energy levels.From the perspective of macroscopic view, individual nuclear spin Distribution produce overall magnetization, it can deviate poised state by the electromagnetic pulse (RF pulses) of application appropriate frequency, make The precessional motion performed on z-axis must be magnetized.Precessional motion describes the surface of circular cone, and the angular aperture of the circular cone is referred to as turning over Corner.The amplitude of flip angle depends on intensity and the duration of the electromagnetic pulse of application.In the situation of so-called 90 ° of pulses Under, spin and deflect into transverse plane (90 ° of flip angle) from z-axis.
After RF pulse terminations, magnetization relaxation returns to original poised state, wherein, the magnetization on z directions is with first Time constant T1(spin lattice or longitudinal relaxation time) is established again, and the magnetization on the direction in z directions with Second time constant T2(spin-spin or T2) relaxation.RF coils can be received by means of one or more to come Magnetized change is detected, the reception RF coils are arranged simultaneously in a manner of the measurement magnetization change on the direction perpendicular to z-axis Orientation is in the inspection volume of MR equipment.After the application of the pulse at such as 90 °, the decay of cross magnetization is accompanied by from phase The order state of same-phase is evenly distributed the transition of the nuclear spin of the state of (dephasing) to all phase angles wherein (by part What magnetic field bump was induced).Dephasing can be compensated by means of refocusing pulse (for example, 180 ° of pulses).This is receiving line Echo-signal (spin echo) is produced in circle.
In order to realize the spatial resolution in body, it is superimposed on uniformly along the linear magnetic field gradient of three main shaft extensions On magnetic field, so as to cause the linear space dependence of spin resonance frequency.Then, the signal picked up in receiving coil includes can With the component of the different frequency associated with the diverse location in body.The MR signal datas obtained via RF coils correspond to sky Between frequency domain, and be referred to as k-space data.K-space data generally includes a plurality of line gathered using different phase codes.Often Bar line is digitized by collecting multiple samples.The set of k-space data is by means of Fourier transformation or other appropriate reconstructions Algorithm is converted into MR images.
Usually need T2Weighting is contrasted to characterize in MR images the tissue damage that (such as in myocardium MR imagings) detects, because For the type depending on damage, tissue has short T2Relaxation time, and therefore in T2Shown as in weighted MR image dark.
T is gathered usually using spin echo (SE) or FSE (TSE) imaging sequence2Weighted MR image.It is standby Select scheme mainly to magnetize and prepare Turbo Field Echo (TFE) technology, wherein, magnetization prepares sequence by encouraging RF pulses to make nuclear-magnetism Change and enter in transverse plane, by one or several refocusing RF pulses by the cross magnetization refocusing, and eventually through right The cross magnetization of refocusing is brought back to z-axis by (tip-up) the RF pulses of digging answered.During the period of cross magnetization, i.e., in T2 Prepare sequence initial excitation RF pulse and it is last dig RF pulses between, T2Decay is provided and is stored in by digging RF pulses Desired T on z directions2Weighting.The such T read with reference to TFE2Preparation can be designated as T2prep-TFE.T2prep- TFE is known in the art for some special applications, such as heart/coronary artery MRI, wherein, spin-echo sequence is less Favorably.
It is well known, however, that T2The problem of preparation scheme is in no T2Interference signal contribution in the case of weighting.These are produced In in T2Prepare sequence afterwards due to T1The increased longitudinal magnetization of relaxation.Such non-T of the MR signals gathered2Weighting is dirty Dye causes the poor T for rebuilding MR images2Contrast.E.R.Jensita et al. the article in MRM 70 (2013) 1360-68 “Motion and flow insensitive adiabatic T2-preparation modula for cardiac MR The Tesla of imagining at 3 " refer to T2Preparation module, the T2Preparation module makes longitudinal magnetization be in depending on its T2's In state.
The content of the invention
According to foregoing teachings, it is readily appreciated that, exist to utilizing T2Weighting carries out the needs of the improved method of MR imagings. The purpose of the present invention is to realize to there is no to come from do not have T2The T of the interference contribution of the MR signals of weighting2Weight MR imagings.
According to the present invention, disclose a kind of to the side for the object progress MR imagings being located in the inspection volume of MR equipment Method, method of the invention comprise the following steps：
A) object is made to be subjected to the first T2Prepare sequence, the first T2Preparing sequence includes excitation RF pulses, one or more Refocusing RF pulses and dig RF pulses；
B) object is made to be subjected to the first reading sequence, the first reading sequence includes at least one excitation RF pulses and shear Magnetic field gradient, for gather MR signals first set；
C) object is made to be subjected to the 2nd T2Prepare sequence, the 2nd T2Preparing sequence includes excitation RF pulses, one or more Refocusing RF pulses and RF pulses are dug, wherein, the 2nd T2Prepare sequence RF pulses in it is at least one have with First T2Prepare the different phase of the corresponding RF pulses of sequence；
D) object is made to be subjected to the second reading sequence, the second reading sequence includes at least one excitation RF pulses and shear Magnetic field gradient, for gather MR signals second set；
E) MR images are rebuild according to the first set of MR signals and second set.
The present invention's sees clearly and is, the first and second T2Prepare the phase of the RF pulses of sequence influences by first and the respectively Two read the phase of the MR signals of sequence acquisition, while they do not influence the interference signal tribute as caused by increased longitudinal magnetization Offer.Therefore, can be according to the present invention, by the first set and the second collection of the MR signals being incorporated in the MR images finally rebuild The first and second T with out of phase are applied in the appropriate superposition closed2Prepare the RF pulses of sequence, to eliminate interference signal tribute Offer.
In other words, the present invention proposes to change in T with reference to the correct combination of gathered MR signals2RF arteries and veins during preparation At least one phase in punching, to add desired (T2Weighting) MR component of signals, while eliminate undesirable (non-T2Weighting) MR component of signals.That is, in T2Prepare the different RF phases in sequence in T2Produce and gathered in different readings after preparation Magnetic resonance signal different RF phases.This allows to distinguish magnetic resonance signal and these readings so that can eliminate and come from Non- T2The interference of weighted components.This can be completed in the reconstruction.
Fully sampled the of MR signals need not be gathered in the step a) of the method for the present invention repeats to single d) One set and second set.On the contrary, before rebuilding MR images completely according to the MR signal datas of collection in step e), Ke Yichong Multiple step a) is answered to d) to be sampled to given k-space region.
In a preferred embodiment, the first and second T2The excitation RF pulses for preparing sequence have a different phases, and first With the 2nd T2The other corresponding RF pulses for preparing sequence have identical phase.In other words, the phase of RF pulses is only encouraged to become Change, and T2The phase for preparing the remaining RF pulses of sequence keeps constant.Most preferably, the first and second T2Prepare swashing for sequence Encouraging RF pulses has opposite phase, it means that the first and second T2Prepare the phase difference of the excitation RF pulses of sequence substantially For 180 °.This produces the first set and second set of the MR signals with contrary sign, and by increasing during MR signal acquisitions The symbol of interference MR signals keeps identical caused by the longitudinal magnetization added.Therefore, can be simply by by the first of MR signals Set and second set are subtracted to eliminate interference MR signals, and to form the set of difference MR signals, MR images are rebuild according to it.It is standby Selection of land, the first MR images can be rebuild according to the first set of MR signals, and can be rebuild according to the second set of MR signals 2nd MR images, wherein, the first and second MR images are subtracted to form difference MR images.In other words, can be in k-space or figure Subtracting to eliminate undesirable signal contribution for MR data is performed in image space.
In an alternative embodiment, such as, thus it is possible to vary T2Prepare the phase for digging RF pulses of sequence.It is also possible to be one Or 90 ° of phase shifts of some refocusing RF pulses.
According to another preferred embodiment of the invention, the first and second reading sequences are gradin-echos, preferably TFE (Turbo Field Echo) sequence.This cause the present invention method be very suitable for special applications, such as such as heart/coronary artery MR into Picture, wherein, spin-echo sequence is less favourable.
Preferably, the first and second T2It is spatially non-selective to prepare sequence.This means in the first and second T2 Prepare the corresponding excitation RF pulses of sequence, refocusing RF pulses and dig RF pulses radiation during magnetic field gradient is not present. Without quick shear magnetic field gradient, method of the invention realizes silent operation.
Recently, the silent MR imagings of the technology to being imaged by such as zero echo time (ZTE) have very big interest.This hair Bright method by ZTE imagings or similar silent imaging technique especially suitable for generating T2Weighted MR image.In ZTE technologies In, with high bandwidth and therefore before the excitation of short, hard excitation RF pulses magnetic resonance, readout gradient is being set.With this side Formula, gradient coding are immediately begun in the excitation of magnetic resonance.In the spoke for the RF pulses for causing effective zero " echo time " (TE) The collection to free inbroduction decay (FID) signal is immediately begun to after penetrating.After FID readings, next RF pulses can applied Before, it is only necessary to which minimum time sets next readout gradient, so as to realizing the very short repetition time (TR).Readout direction from Repeat to repetition to gradually change, until the spherical volume in k-space is sampled required degree.TR intervals need not closed Between readout gradient in the case of, almost can silently perform ZTE imaging.Therefore, the first and second readings of the invention Sequence can be zero echo time sequence, each include：
I) set with readout direction and read the reading magnetic field gradient of intensity；
Ii) the radiation excitation RF pulses in the case where reading magnetic field gradient be present；
Iii FID signal) is gathered in the case where reading magnetic field gradient be present, wherein, FID signal represents radial direction k-space sample This；
Iv readout direction) is gradually changed；
V) by repeat step i) to iv) repeatedly the spherical volume in k-space sampled, wherein, gathered FID signal forms the first set and second set of MR signals respectively.
The method of the invention described so far can be performed by means of a kind of MR equipment, and the MR equipment includes：Extremely A few main magnet coil, it is used to generate uniform stabilizing magnetic field in inspection volume；Multiple gradient coils, it is used in institute State the magnetic field gradient that shear is generated on the different spaces direction in inspection volume；At least one RF coils, it is used in the inspection Generation RF pulses and/or the body for the patient from positioned at the inspection volume receive MR signals in product of having a medical check-up；Control is single Member, it is used for the magnetic field gradient of continuous RF pulses and shear in control time；And reconstruction unit.The method of the present invention is preferred Implemented by the reconstruction unit of MR equipment and/or the corresponding programming of control unit on ground.
The method of the present invention can be performed advantageously in most of MR equipment of current Clinical practice.On the other hand, only need The computer program for controlling MR equipment is utilized, it is performed the above method step of the present invention.Computer program may have In in data medium or being present in data network, so as to download in the control unit of MR equipment.
Brief description of the drawings
Accompanying drawing discloses the preferred embodiments of the present invention.It will be appreciated, however, that accompanying drawing is designed to the mesh being merely to illustrate , not as the definition of the limitation of the present invention.In figure：
Fig. 1 schematically shows the MR equipment of the method for performing the present invention；
Fig. 2 shows the T of the diagram present invention2Weight the figure of MR Irnaging procedures.
Embodiment
With reference to figure 1, the MR equipment 1 that can be used in performing the method for the present invention is shown.The equipment includes superconduction or electricity Resistive main magnet coil 2 so that along z-axis by checking that volume creates main field B constant on the substantially uniform, time0。 The equipment also includes the set 2 ' of (single order, second order and-- three rank under applicable circumstances) shim coil, wherein, for most Smallization checks the B in volume0The purpose of deviation, the electric current by the individual shim coil of set 2 ' is controllable.
Magnetic resonance generation and steerable system invert or excited nuclear magnetization using a series of magnetic field gradient of RF pulses and shear Spin, magnetic resonance is induced, refocusing magnetic resonance, magnetic resonance is manipulated, spatially and otherwise coding magnetic resonance, spin is satisfied With etc., to perform MR imagings.
More specifically, x, y and z axes of the Gradient pulse amplifiers 3 along inspection volume are into whole-body gradient coil 4,5 and 6 Selected coil applied current pulse.Digital RF frequency transmitter 7 switchs 8 by RF pulses or pulse bag via transmission/reception Body RF coils 9 are sent to, RF pulses are sent to and checked in volume.Typical MR imaging sequences include what is taken together each other The bag of the RF pulse segments of short duration, and the magnetic field gradient of any application realizes the selected manipulation of nuclear magnetic resonance.RF Pulse is used to carry out saturation, excitation resonance, reverse magnetization, refocusing magnetic resonance or manipulation resonance, and selects to be positioned in inspection The part of body 10 in volume.MR signals are also picked up by body RF coils 9.
In order to be generated the MR images in the region of the limitation of body 10 by means of parallel imaging, by local RF coil 11,12,13 Set be disposed adjacent in be selected for imaging region.Array coil 11,12,13 can be used to receive by body coil RF sends the MR signals of induction.
Obtained MR signals pick up and by preferably including by body RF coils 9 and/or by array RF coils 11,12,13 The receiver 14 of preamplifier (not shown) demodulates.Receiver 14 via transmission/reception switch 8 be connected to RF coils 9,11, 12 and 13.
The control of master computer 15 passes through shim coil 2 ' and the electric current of Gradient pulse amplifiers 3 and transmitter 7 to generate According to the imaging sequence of the present invention.Each RF driving pulses are followed, receiver 14 in extremely rapid succession receives a plurality of MR data wires.Number The analog-to-digital conversion of signal to receiving is performed according to acquisition system 16 and be suitable for further place by every MR data line transitions The number format of reason.In modern MR equipment, data collecting system 16 is independent computer, and it is exclusively used in raw image data Collection.
Finally, it is figure by digital original image data reconstruction by the reconstruction processor 17 of the appropriate algorithm for reconstructing of application As representing.Then, store the image in video memory, wherein, it can be accessed, for for example via provide to The video-frequency monitor 18 of the human-readable display of the MR images arrived, by the projection of graphical representation or other parts be converted into be used for can Depending on the appropriate format of change.
Fig. 2 shows the figure of the Irnaging procedures of the diagram present invention.Methods described starts from the first T2Prepare sequence T2PREP1, it includes encouraging 21, two refocusing RF pulses 22 of RF pulses and digs RF pulses 23.Hereafter, using as ZTE The first of sequence reads sequence RO1.Readout gradient is set (not paint before the radiation of short, hard, small flip angle excitation RF pulses System).After the radiation of excitation RF pulses, immediately begin to gather free induction decay (FID) signal.After FID readings, Next readout gradient, etc. is set before the next hard excitation RF pulses of application.Readout direction gradually changes from repetition is repeated to, Until the spherical volume in k-space is sampled required degree.The FID signal gathered during the first reading sequence RO1 is formed The first set of MR signals.The first set of MR signals includes T2Weighted signal contributes 24 and by during MR signal acquisition Interference signal contribution 25 caused by increased longitudinal magnetization.As next step, using the 2nd T including encouraging RF pulses 21 '2 Prepare sequence T2PREP2.Excitation RF pulses 21 and 21 ' have opposite phase (i.e. 180 ° of phase differences).2nd T2Prepare sequence Row T2PREP2 uses the refocusing RF pulses 22 ' with same phase and digs RF pulses 23 ', such as the first T2Prepare sequence T2PREP1 corresponding RF pulses.In second reads sequence RO2, the second set of MR signals is gathered, it includes T2Weighted components 24 ' and the interference components 25 ' as caused by increased longitudinal magnetization.With the first set of identical readout direction collection MR signals And second set.T2Weighting MR component of signals 24 and 24 ' have opposite symbol, and disturb the symbol of MR signal contributions 25,25 ' It is identical in two collections RO1, RO2.Curve 24,24 ', 25,25 ' schematically illustrates reads sequence first and second Arrange RO1, RO2 during as time t function corresponding MR signal contributions amplitude.By by the first set of MR signals and Two set are subtracted to eliminate interference MR signal contributions 25,25 ', to form the set of difference MR signals, are finally believed according to difference MR Number set rebuild MR images.Therefore, final MR images are complete T2Weighting, not from non-T2Weight MR signals point Any contribution of amount.

Claims (11)

  1. Carry out MR imaging methods to the object that is located in the inspections volume of MR equipment (1) 1. a kind of, methods described including with Lower step：
    A) object (10) is made to be subjected to the first T2Prepare sequence (T2PREP1), the first T2Preparing sequence includes excitation RF arteries and veins Rush (21), one or more refocusing RF pulses (22) and dig RF pulses (23)；
    B) object (10) is made to be subjected to the first reading sequence (RO1), the first reading sequence includes at least one excitation RF Pulse and the magnetic field gradient of shear, for gathering the first set of MR signals；
    C) object (10) is made to be subjected to the 2nd T2Prepare sequence (T2PREP2), the 2nd T2Preparing sequence includes excitation RF arteries and veins Rush (21 '), one or more refocusing RF pulses (22 ') and dig RF pulses (23 '), wherein, the 2nd T2Prepare sequence Arrange (T2PREP2) the RF pulses (21 ', 22 ', 23 ') in it is at least one have and the first T2Prepare sequence (T2PREP1) the different phase of corresponding RF pulses (21,22,23)；
    D) object (10) is made to be subjected to the second reading sequence (RO2), the second reading sequence includes at least one excitation RF Pulse and the magnetic field gradient of shear, for gathering the second set of MR signals；
    E) MR images are rebuild according to the first set of MR signals and the second set.
  2. 2. the method according to claim 11, wherein, the first T2Prepare the excitation RF pulses of sequence (T2PREP1) And the 2nd T (21)2The excitation RF pulses (21 ') for preparing sequence (T2PREP2) have different phases.
  3. 3. method according to claim 1 or 2, wherein, rebuild in step e) before the MR images, step a) is to d) It is repeated quickly and easily as many times as required to be sampled to given k-space region.
  4. 4. according to the method described in any one of claim 1-3, wherein, the first T2Prepare sequence (T2PREP1) and institute State the 2nd T2It is spatially non-selective to prepare sequence (T2PREP2).
  5. 5. according to the method described in any one of claim 1-4, wherein, the first T2Prepare the institute of sequence (T2PREP1) State excitation RF pulses (21) and the 2nd T2The excitation RF pulses (21 ') for preparing sequence (T2PREP2) have conversely Phase.
  6. 6. according to the method for claim 5, wherein, by the first set of MR signals and the second set subtract with The set of difference MR signals is formed, wherein, the MR images are the collection occlusal reconstructions according to the difference MR signals.
  7. 7. according to the method for claim 5, wherein, the first MR images are rebuild according to the first set of MR signals , and the 2nd MR images are rebuild according to the second set of MR signals, wherein, the first MR images and the 2nd MR are schemed Image subtraction is to form difference MR images.
  8. 8. according to the method described in any one of claim 1-7, wherein, described first, which reads sequence and described second, reads Sequence is gradin-echo, preferably TFE sequences.
  9. 9. according to the method described in any one of claim 1-7, wherein, described first, which reads sequence and described second, reads Sequence is zero echo time sequence, is each included in the first reading sequence and the second reading sequence：
    I) set with readout direction and read the reading magnetic field gradient of intensity；
    Ii the excitation RF pulses) are radiated in the case where the reading magnetic field gradient be present；
    Iii FID signal) is gathered in the case where the reading magnetic field gradient be present, wherein, the FID signal represents that radial direction k is empty Between sample；
    Iv the readout direction) is gradually changed；
    V) by by step i) to iv) repeatedly the spherical volume in k-space is sampled, wherein, the FID gathered Signal forms the first set of MR signals and the second set respectively.
  10. 10. a kind of MR equipment, including：At least one main magnet coil (2), its be used to generate check it is uniform, stably in volume Magnetic field；Multiple gradient coils (4,5,6), it is used for the magnetic for generating the shear on the different spaces direction in the inspection volume Field gradient；At least one RF coils (9), it is used for the RF pulses generated in the inspection volume and/or comes from quilt for receiving The MR signals for the object (10) being positioned in the inspection volume；Control unit (15), it is used to controlling RF pulses and shear The time succession of magnetic field gradient；And reconstruction unit (17), wherein, the MR equipment (1) is arranged to perform following steps：
    A) object (10) is made to be subjected to the first T2Prepare sequence (T2PREP1), the first T2Preparing sequence includes excitation RF arteries and veins Rush (21), one or more refocusing RF pulses (22) and dig RF pulses (23)；
    B) object (10) is made to be subjected to the first reading sequence (RO1), the first reading sequence includes at least one excitation RF Pulse and the magnetic field gradient of shear, for gathering the first set of MR signals；
    C) object (10) is made to be subjected to the 2nd T2Prepare sequence (T2PREP2), the 2nd T2Preparing sequence includes excitation RF arteries and veins Rush (21 '), one or more refocusing RF pulses (22 ') and dig RF pulses (23 '), wherein, the 2nd T2Prepare sequence Arrange (T2PREP2) the RF pulses (21 ', 22 ', 23 ') in it is at least one have and the first T2Prepare sequence (T2PREP1) the different phase of corresponding RF pulses (21,22,23)；
    D) object (10) is made to be subjected to the second reading sequence (RO2), the second reading sequence includes at least one excitation RF Pulse and the magnetic field gradient of shear, for gathering the second set of MR signals；
    E) MR images are rebuild according to the first set of MR signals and the second set.
  11. 11. a kind of computer program to be run in MR equipment, the computer program includes the instruction for following operation：
    A) the first T is generated2Prepare sequence (T2PREP1), the first T2Prepare sequence include excitation RF pulses (21), one or Multiple refocusing RF pulses (22) and dig RF pulses (23)；
    B) generation first reads sequence (RO1), and described first, which reads sequence, includes the magnetic of at least one excitation RF pulses and shear Field gradient, for gathering the first set of MR signals；
    C) the 2nd T is generated2Prepare sequence (T2PREP2), the 2nd T2Prepare sequence include excitation RF pulses (21 '), one or Multiple refocusing RF pulses (22 ') and RF pulses (23 ') are dug, wherein, the 2nd T2Prepare the institute of sequence (T2PREP2) State in RF pulses (21 ', 22 ', 23 ') it is at least one have and the first T2Prepare the corresponding RF arteries and veins of sequence (T2PREP1) Rush (21,22,23) different phase；
    D) generation second reads sequence (RO2), and described second, which reads sequence, includes the magnetic of at least one excitation RF pulses and shear Field gradient, for gathering the second set of MR signals；
    E) MR images are rebuild according to the first set of MR signals and the second set.
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